An ACT candidate is taking legal action against the Engineering, Printing and Manufacturing Union after being sacked for standing in the forthcoming election.
Shawn Tan was suspended from his job last month after ACT announced he was 10th on its party list.
Employment advocate Max Whitehead says Mr Tan was dismissed on Tuesday night after a fourth meeting to discuss his position.
He says Mr Tan has already lodged a personal grievance and will now lodge an unjustified dismissal claim.
Mr Whitehead says the union has no right to discriminate against someone based on his or her political opinions.
He says what his client does in his own time is his own business - provided it does not interfere with his work.
The union says it sacked Mr Tan after deciding his actions had irrevocably damaged their employment relationship.
National secretary Andrew Little says the issue of Mr Tan's candidacy was never about his political affiliations, but about his obligations to the union.
Mr Tan was previously suspended on full pay.
The union says two other employees have sought approval to stand for public office this year. One was declined and the other was approved.